Master Quest changed the puzzles inside all the dungeons in Ocarina of Time, and the 3DS version is also mirrored.

The puzzles aren't as good as the original puzzles, but it's fun to play as an alternate take on the game. It's almost like 1999-era DLC, given it was originally planned for the 64DD in Japan.

A shame the DD add-on was Japan only. I was really interested in the F-Zero X tracks added in particular. Just like sadly the SNES Satellaview was not released outside of Japan and I've always wanted to try ou F-Zero 2.